The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Within the structure of rotors for turbine generators, a number of components are secured within a longitudinal slot around and on top of the electrical windings. These components serve functions to insulate and secure the electrical windings within the rotor slot, interact with the rotating magnetic field, and also to provide for the passage of cooling gases through passageways in the components. Among the components within a rotor body or housing slot are electrical windings/coils (also referred to as “copper turns” in the industry), creepage members, amortisseurs, springs, and wedges. Generally, the creepage members provide electrical insulation or dielectric separation from the copper turns, the amortisseurs reduce or eliminate the possibility of axial current flow, and the springs provide a radial force to press the amortisseurs against the wedges, which hold the components within the slot.
Each of the components within the slot includes a series of openings or vent holes, which facilitate radial cooling by the flow of cooling gases. The openings in each of the components, when properly installed within the rotor slot, are aligned with each other in order to provide for an unobstructed and efficient flow of cooling gas. Often times, however, because of the heating and cooling cycles of the generator rotor, among other causes, the components within the rotor slot migrate outwardly over time, which causes the openings to be misaligned, thus blocking the flow of cooling gas. This blockage of the cooling passageways is undesirable for efficient and continuous operation of the rotor.
An exemplary rotor and the misalignment issue as described above are disclosed in U.S. Application No. 2013/0221797 titled “Amortisseur Assembly and Apparatus to Maintain Radial Venting Hole Alignment.” As shown in FIG. 1 of this application, the rotor 1 includes slots 2 with vent holes opening to radial vent paths 3. Also shown is a retaining ring 4, which generally holds the components as described above within their respective longitudinal slots.
FIGS. 2A-2D illustrate the issue of spring migration where a number of slot springs 5 have migrated outwardly from their nominal positions due to the heating and cooling cycles of the rotor during and between operation. Also shown in these figures are the electrical windings/coils 6, the creepage members 7, amortisseurs 8, wedges 9, vent holes 10 (which are misaligned as best shown in FIG. 2B), and the rotor body 11 containing the slots that house these components. The retaining ring as mentioned above is removed for clarity in these figures. Spring migration is undesirable because of the associated reduced operating output, vibration effects and down-time.